The present invention relates to an apparatus and a method of controlling a mobile body, and a mobile body system.
A synchronous motor that uses a permanent magnet to create a magnetic field has recently been applied to various mechanical apparatuses for the purpose of reducing the size of the apparatuses and increasing efficiency.
However, in order to control rotation of a synchronous motor, it is necessary to recognize the position of a rotor, i.e. a magnetic pole position, and to control power supply. To do so, means for detecting a magnetic pole position is required. For example, the prior art disclosed in Japanese Application Patent Laid-Open Publication No. Hei 10-80188 requires a magnetic pole position sensor. This kind of magnetic pole position detector requires effort to align a motor shaft with an encoder shaft or complicated, painstaking maintenance.
To eliminate such problems, there have been some studies of technology to control a magnetic pole position of a synchronous motor without using a sensor, as described in Proceedings of the 2000 Japan Industry Applications Society Conference ″No.97: A New Position Sensor-less Control of Permanent Magnet Synchronous Motor using Direct Position Error Estimation, Pages 963–966.
FIG. 10 illustrates an example of a permanent magnet-type synchronous motor control system in accordance with the magnetic pole position sensor-less control technology. This control system comprises a first coordinate transformer 3a which obtains detected current values Id and Iq of a rotating coordinate system by inputting motor phase detected current values Iu and Iw detected by a current detector, an axis error estimator 3b which obtains an error Δθ between a magnetic pole position θm of a motor rotor and an estimated magnetic pole position value θmc by inputting the detected current values Id and Iq, a motor speed computing element 3c which obtains estimated motor speed ωm by inputting the error Δθ, a rotor position estimator 3d which obtains an estimated magnetic pole position value omc by inputting the estimated motor speed ωm, a current command computing element 3e which obtains current command values Id* and Iq* by inputting the estimated motor speed ωm and a motor speed command value ωm*, an output voltage command computing element 3f which obtains output voltage commands Vd* and Vq* by inputting the current command values Id* and Iq*, and a second coordinate transformer 3g which obtains drive unit drive commands Vu*, Vv* and Vw* for driving the motor by inputting the output voltage commands Vd* and Vq*. This example uses an estimated value θmc obtained by a rotor position estimator 3d as a magnetic pole position em so that a permanent magnet-type synchronous motor can be driven without requiring a magnetic pole position sensor.
Technology mentioned above has made it possible to rotate a synchronous motor without requiring a detector which detects a magnetic pole position of the rotor.
For example, in Japanese Application Patent Laid-Open Publication No. 2000-78878, an example of an actual mobile body system is shown that applies the sensor-less control technology for controlling a magnetic pole position of a synchronous motor. However, this example requires an encoder as a mobile body position detector so that the mobile body system itself can be controlled to stop at a fixed point.